Abstract:

In the context of climate change and increasingly intensive human activities， the evaluation of ecosystem service functions has become one of the primary research directions in Earth sciences. In particular， the continuous improvement of the integration between the InVEST model and ArcGIS has made it possible to assess ecosystem service functions， such as water conservation， soil retention， windbreak and sand fixation， and carbon sequestration. These assessments have become critical references for regional sustainable development planning. This study combines the InVEST model with the spatial analysis module of ArcGIS to analyze the impact of geomorphic differentiation on both independent and integrated ecosystem service functions in the Xiliugou watershed. It also explains changes in the ecosystem service functions over the past three decades. The results showed that： geomorphic type spatial differentiation has a significant impact on ecosystem service functions. Between 1990 and 2020， water conservation increased by 4.62 mm， with the largest increase （2.55 times） occurring in desert areas； soil retention decreased by 22.62 t·hm^-2·a^-1， with the most significant reduction （30.44 t·hm^-2·a^-1） observed in loess regions； deposit by windbreak and sand fixation increased by 1.30 t·hm^-2·a^-1， with the largest increase （1.7 t·hm^-2·a^-1） in desert areas； and carbon sequestration increased by 0.08 t·hm^-2·a^-1， with the most notable increase （0.22 t·hm^-2·a^-1） in loess regions. The comprehensive evaluation pattern analysis revealed that higher-level types occupy the largest distribution areas at different time points. The spatial pattern characteristics of different levels are marked by the concentration of lower-level types in desert areas in 1990 and the concentration of higher-level types in loess and plain areas in 2020. Changes caused by geomorphic differentiation in the study area were most pronounced in loess and desert regions. Overall， high and higher-level areas increased by 138.1 t·hm^-2·a^-1 and 213.6 t·hm^-2·a^-1， respectively， while low， lower， and medium-level areas decreased by 7.5 t·hm^-2·a^-1， 235.0 t·hm^-2·a^-1， and 109.1 t·hm^-2·a^-1， respectively. The changes in ecosystem service functions in the Xiuliugou watershed are closely related to ecological engineering projects implemented over the past three decades， including soil and water conservation efforts with scientific rotational grazing in the loess area， and integrated management and utilization of Kubuqi desertification.

Key words: ecosystem services, assessment, InVEST model, Xiliugou